Ultra high frequency oscillator of the cavity resonator type



J. M. LAFFERTY ULTRA HIGH FREQUENCY OSCILLATOR Of THE CAVITY RESONATOR TYPE Filed 001;. 2. 1942 lnvenfiorz James M. Laffer'by Jo W 6?) y 'His Attorney Patented July 1, 1947 UNITED STAT ULTRA HIGH FREQUENCY OSCILLATOR OF THE CAVITY RESONATOR TYPE James M. Lafierty, Colonic, N. Y., assignor to General Electric. Company, a corporation: of

New York Application October '2, 1942, Serial'No.-- 460,524.-

14 Claims.

My invention relates to. electric discharge devices and more particularly to ultra high frequency electric discharge devices of the. space resonant type.

With the ever increasing demand for electric discharge apparatus anddevices for use in the ultra high frequency field, it has become apparent that many of the prior art arrangements are not'satisfactory due primarily to the prohibitive decrease in the input impedance thereof as the operating frequency is increased. In accordance-with the teachingsof my invention described hereinafter, I provide a new and improved electric discharge device which is capable of operation satisfactorily within theultra high frequency field, and which obviates many'of the disadvantages of the prior art arrangements.

It is an. object of my invention toprovide a new and improved electric discharge device.

It is another object of my-inventionto provide a new and improvedhigh frequency oscillatorand amplifier of the space resonant type.

It i a further object. of my invention to provide a new and improved ultra high frequency triode oscillator or amplifier of. the space reso-. nant type comprising a space resonant cavity, or cavities, which may be considered as comprising isolated sections of a dielectric wave-guide.

It is a still further object of. my invention to provide anew. and improved ultra highfrequency triode oscillator of thespace resonant typecomprising. a plurality of adjoining and metallically bound tuned space resonant cavities, andwhich includes means therein forefiecting aconcentration ofthe potential differences due to the.electroinagnetic waves within the respective. cavities and which is provided. with anelectricdischarge path which maintains the discharge device in os cillation.

Brieflystated, in accordancewith the illustrated embodiment ofmy invention,.I.provide a new and. improved high. frequency electric discharge device, such as a high-frequency triode .oscillator ,.which..ccmprises a pair of adjoining,.metallically bound, space resonant cavities which. are

dimensioned tosupport electromagnetic waves of predetermined frequency. The cavities have a metallicboundary in common and this boundary provided with a communicating. opening.

Means, such as a resonant aperture or slot, is i provided in transverse-wall sections in each of the cavities to effect a concentration of the potential difference due to the electromagnetic waves, or the 'standing electromagnetic waves, in each of the cavities, and electric discharge means is associated with the opening in the metallic boundary. and the resonant apertures to produce and maintain oscillation of the electric discharge device as a whole, so that energy may be derived from eitherone of the cavities. I In, accordance with another feature of *my' invention, I provide a new andimp'roved'high fre-- quency amplifierof the space resonant type which comprises'two tuned cavities or sections ofahollow-pipe type dielectric-wave guide each of which includes means, such as a resonant'aperture or slot, for concentrating the voltage'difl e'rence due to the electromagnetic waves andassociated controlled'discharge path." Input electrode means are associated with the grid cathode cavity' and output electrode means are associated 'withthe anode-grid cavity. a a a v The subject matter of this application relates to improvements in electric discharge devices of the space resonant type of the nature disclosed and broadly claimed in my copending UpSi'pat ent application, Serial No. 460,523, filed concur rently herewith and which is assigned to'the as= signee of thepresent application.

For a better understanding or my invention, reference may be had to the following-description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. Fig. 1' diagrammatically illustrates a longitudinal cross sectionalview'of a high frequency triode oscillator built in accordance with my invention; Fig. 2 is a cross-sectional end view particularly relating to the transverse wall sections including-the resonant apertures and the associated anode and cathode which constitute an electric-discharge path; and Fig. 3 is a modification of my invention as applied'to a high frequencyamplifier of the space resonant type.

As statedabove, employed in the electric discharge device which I provide may be considered as isolated or tuned sections of a-dielectric wave guide of the hollowpipe type. Accordingly, iii iseb'elieved that it may be helpful in the description of my invention to review briefly-certain.fundamental aspects of dielectric waveguidesof the hollow-pipe type.

It is now somewhat generally. appreciated that high frequency electromagnetic waves may be transmitted'through or supported by "dielectric wave guides of the hollow-pipe type, such as wave guides constructed of" a highly conductive material or metal such as copper or brass, where the frequency at which the guide is eXcite'd'is greater than the critical or cut-off frequency. The'ty'pes the space resonant cavities of waves which may be transmitted dielectrically through guides of this type are manifold and heretofore have been generally classified into the E and H types. Although my invention may be applied to electromagnetic waves of a variety of types, in the following description particular ref erence will be made to the H01 type of wave inasmuch as it is of less complex order and mode and inasmuch as it is easier to produce this type of wave and utilize it than some of the higher order waves.

Where the dielectric wave guide or a section thereof is excited at a frequency greater than the critical or minimum frequency, the wave will be propagated through the dielectric guide having a rectangular cross section of height a and base b, and will have a phase constant c which may be expressed as follows:

i -eiieir where w is the angular velocity of the wave propagated through the medium; that is, w is equal to 21, where f is the frequency of the wave, or in the case of a cavity it is the natural frequency of the cavity, ,u1 is the permeability of the medium within the guide or cavity; 61 is the effective dielectric constant of the medium, and n and m are, respectively, the order and mode of propagation of the electromagnetic wave under consideration.

It will be noted that in Equation 1 61 is defined as being the effective dielectric constant of the'medium. As will be described presently, the electric discharge devices which I provide include as an element thereof an electric discharge path, that is a region of charged electrical particles, which aifect the, dielectric constant of the medium within the cavities. More particularly, the-presence of the charged electrical particles, such as electrons, effect a reduction in the magnitude of the dielectric constant of the medium and as a result affect the phase constant 5 and the phase wave length of the electromagnetic waves supported by the respective cavities, Accordingly, it is necessary in the computation of thejphase constant and the phase wave length to employ the effective value of the dielectric con stant of the medium as modified by the presence of the region of charged particles. Generally speaking, it may be said that the eifective dielectric constant of the medium is a function of the difference of the dielectric constant of the medium with no charged particles present, a quantity which is directly proportional to the number of charged particles per unit volume, the square of the unit charge of each particle, and inversely proportional to the mass of each charge and some function of the frequency,

' The critical frequency in may be defined as follows:

1 f0 2% a b l Referring now to Fig l of the accompanying drawing, I have there diagrammatically illustrated my invention as applied to an electric discharge device, such as a high frequency triode oscillator which comprises a pair of tuned or space resonant cavities I and 2 of the hollowof the cavities may be defined by metallic plates 6 and l, and the sides shown in Fig. 2 may all be welded or soldered to form a hermetically sealed region.

The longitudinal dimension of the space resonant cavities I and 2 is established to be an integral multiple, either odd or even, of a half- Wave length of the electromagnetic Wave which would be propagated through the cavities if these cavities constitutedsections of a dielectric wave guide of the hollow-pipe type. Consequently, one value of longitudinal dimension chosen may be where A is defined by Equation 3 above.

The common metallic boundary 3 is provided with an opening 8 which serves as a communicating path between the cavities and which permits the establishment of an electric discharge to be described presently.

Within each of the tuned cavities I and 2, I provide means for accentuating or concentrating the potential difference due to the electromagnetic waves within the respective cavities. This means may comprise a Wall structure which provides tuned or resonant apertures, such as resonant slots, tuned substantially to the natural frequency of the cavities. For example, I provide within cavities I and 2 a transverse wall section comprising metallic walls or partitions 9, I0, II and I2, also shown in Fig. 2, which in conjunction with the metallic boundary plate 3 define resonant apertures or slots I3 and I l having a height h and a principal dimension or length L. The apertures, in any case, should have an appreciable dimension substantially transverse to the electric component of the electromagnetic field within the cavities and byvirtue of their dimensions are resonant, that is, have an efiective distributed inductance and capacitance thereby establishing natural resonance frequencies thereof corresponding to the natural frequencies of the respective cavities.

There is a definite relationship between the height h and length L of the resonant apertures in order to obtain this resonant condition, which is important not only from the standpoint of obtaining concentration of the voltage or potential due to the waves within the cavities, but is also of importance in maintainin the transverse wall structures substantially refiectionless so as not to disturb the tuned or resonant characteristics of the cavities. The total impedance Z0 of a dielectric wave guide or a rectangular cavity comprising a section of a dielectric wave guide, using the dielectric medium may be defined as follows:

where e1 is the effective dielectric constant of the medium and c is the velocity of light If this total impedance is constant along the guide, the wave will-not'be'refiected. To maintainthisimpedanoe constant for changes in dimensions wand b; one must-have at anyparticular wave length orfrequencythe followingrelationship:

b (5) Asstatecl above, the apertures 13 and M are resonant. It will be appreciated thatth'enatura'l frequency or; the resonance frequency, or frequencies, oitheaperturesor slots" l-3-a-nd- M will beaiiected'by the dielectric-constant of the medium within which theseslots areplaced. Furthermore, the natural or resonance frequency," or frequencies, of these apertureswill-vary a-sa function of-the effective dielectric constant ofthe m'edium asmodiiiedand established by'thepresenc'e in the'region of chargedelectricalparticles, such as electrons, which constitute the beam transmitted from cathode Hi to anode I 5 Thisvariation inthe dielectric constant will be-appreciated by considering the fact that theefiective distributed capacitanceoithe slots lS'and" M' W-ith an electron beampresent is less than that when nobeam is'present; As a result, in the computation of the'dimensions h and L of the slots 53 and i4, the-effect of the-region-ofcharged particles must be taken into consideration. Viewed as ageneral-matter; it maybe said that for a slot of given heightand'lengt-h, the establishment of a region of'charged particles'will effect a reduction ordecreasein the magnitude of the distrib uterl capacitance of the slot, inasmuch, as is Well known, the capacitance is directly proportional to thedielectricconstant and inversely proportional to'the distances between the surfaces involved. Consequently, if a slot'isd'esigned'to Ice-resonant to an electromagnetic wave of particular frequency with no "region of charged particles pres ent, upon-the establishment of such aregion the efieotive'height or dimension h of'the slot niust be decreased-in order to eiiect a'result'ant capacitance to resonate with the distributed inductance. Stated in other words, theratio'of the dimension It to the length L 'willbedecreased due to'the presence-of the region o'f-charged particles; If the change in guide dimensions isemade in verysmall 1 fraction of a wav'e length ts, there will be a reflection from the discontinuity so' pro duced; but this reflection is inefiective because of a reflection from a second discontinuity a very short phase distance alongthe guide or: cavity from the firstdiscontinuity: By the use era-rec'- k constant 5 k) tangular resonant :slot, .01 the equivalent thereof,

the total impedance of the slot-itself'ismadeto be exactly equal to the total-impedance of .the guide or cavity, since the. reflection produced at the entrance of theslot' is just cancelled by the reflection at the exit.

The above stated relationships: relative 'toithe dimensions It and L to maintain the slot in=a resonant condition obtains irrespective of the position'of the slot in thetransversepartition, In the embodiment of my invention sh'own in Figs. 1 and 2, the resonant apertureslii 'andllareadja cent to and partially defined by the metallic boundary plate 3'.

. I provide electric discharge means for'estahlishing a region of charged particles, such asan electron beam, for maintaining the electric discharge device as a whole in oscillation. The elec-tricidischarge device may comprisean: anode l5 anda thermionic cathode I'B on opposite side'sof the boundary plate 3 and i-n alinement'with thopeni-r ig l. An anode i E-and cathode I'Fmaybemaintained in spaced'srela'tion with respect to each other-fandffrom partitions e, 0 am]; H, l2, respectively, by means: of vitreous sor glass insulators i? and w whichmaybeaof cylindrical cross section. Cathode-rl i-isiprovidedwith a cathodeiheating element I 9; and? anode l5 and cathode it are positioned soth'at :thefaces thereof constitutea longitudinalib'onndary for the resonant slot assembly, the outside-surfaces of these elements b'eingisubstantiallyparallelwith the-defining edges of the openings or partitions 9- l 2, inclusive.

Anode I5 andcathode lfiare electrically insulated' 'not only from the partitionsQ-IZ but are also:ele'ctricallyinsulated from the defining walls of the cavities and Iiprovide sealing glass insulators 20 and 25 which extend throughitop plate 5': and :bottom plate 4; respectively. These "seals, of course; are important'in orderto maintain the cavities atthecle'sire'dlow pressurewhich facilitates tlre-establishment and control of'the'electric dischargeapath; Conductors Z2 and. zit-extend through? the insulators zil and 25' and are conne'cted'to'th'e anode i5" and cathode l5, respectively; 'Asa rneans for modulating or controlling the electron beam, :Iprovideelectrostatic control or grid-means? i' wliich may comp-rise a grid-wire or mesh in spaced relation with respect to anode l5 andcathode it, and which-is preferably conductively. c'onnected to the boundary plate '3.-

As a means'for' supplying power to the electrio-discharge deviceas a whole, I may employ asourceof unidirectional voltage, such as a battery"25,-the-positive-terminal of which is connecte'dto anode l5" and the negative terminal of which is connected 'to cathode Hi. The entire metallic deiining structureofthe discharge device may-beconnected-toground; in which case thevhighfrequency anode potential and cathode potential imay lee-considered as being in timeph'asewith respeot'toueach other; the potential of therfgrid remaining fixed by virtue of the ground connection;

I'provide-means for coupling the cavities 'l and Z'inordei" that energy may be derived from the anode-gridcavity! and delivered to the gridcath'ode' cavity" 2 to maintain the discharge -device-in oscillation. Where the electrostatic control snernher or grid -24 -is maintained at grid potential, causing'th-e' anode and'cathodepotentials t'o vary in time phase with respect to it, the coupling means" between theanode-grid and gridcathode cavities may comprise" a phase-reversing'coupling clevioe, such as a double loop 26, which extends through anopening 21' in the metallic "boundary plate 3. In this manner, the

proper phase between the anode-grid and gridcathode-"cawity "voltages is obtained.

Energy mayme extracted from the cavities of thedischarge'devi'ce by a variety of electrode means for the-purpose of' illustrating one form-of such=meansI have diagrammatically illu'strated the electrode means as comprising a concentric or coaxialtransm-i-ssion line includingz-a tubular conductor 28 and a-concentr'ic conductor 29-,"the latter of'w-hichforms a loop 30 within the anode-grid cavity I; Of course, a sealing insulator, such as a vitreous orglass'insu-lat'or' '3li; may beplaced conductor 28 and sealedto -bothconductors 28' and 29;

The-cathodej'heating element" lfi 'of cathode it maybe provided with externally 'accessibleterminalconductors 3Z- and '33 which are supported by glass-insulators 3'4 and-351' The' embodiment of my invention illustrated in Figs. 1 and 2 operates to supply high frequency electromagnetic waves, the energy of the device being extracted from one of the resonant cavities, such as cavity I, through the concentric transmission line comprising conductors 28 and 29. The energy for the operation of the electric discharge device is derived from battery 25 by the anode-cathode circuit of the electric discharge path including anode l5 and cathode I6. The cyclic or periodic voltages for exciting and maintaining the resonant cavities l and 2 in oscillation are produced by virtue of the control or modulation of the electron beam of the discharge path produced principally by the cyclic variations in the potential of the electrostatic control grid 24.

Due to the fact that the transverse wall assembly comprising partitions 9-10, inclusive, and the associated electric discharge path are located within the vicinity of the potential-maximum or the potential loop, the modulation of the electron beam is effective to produce electromagnetic waves within cavity I which may be considered, for the purposes of elementary analysis, as being generated across the horizontal edges of the resonant slot l3. By virtue of the tuned or resonantnature of cavity I, a standing electro-magnetic wave is maintained therein.

The feed-back or coupling between cavities fl and 2 is obtained by virtue of loop 26; that is, energy is derived from anode-grid cavity I and supplied to grid-cathode cavity 2 in order to maintain the latter mentioned cavity in oscillation. The oscillations which are established within cavity 2 produces a standing electromagnetic wave, the potential-maximum or potential loop of which is in the vicinity of the transverse partitions H and I2, thereby concentrating by the action of resonant slot M the potential difference due to the wave to utilize most effectively this potential difference in the control or modulation of the electron beam by virtue of the electrostatic effect of grid 24. The variation in the potential of grid 2 occasioned by the variation in voltage across the horizontal dimensions of slot l4 modulate the electron beam which, in turn produces cyclic variations of potential across the horizontal dimensions of slot I3, thereby maintaining, by the above described sequence of phenomena, bo h cavities l and '2 in oscillation.

As stated above. where the entire metallic cavity structure, that'is the boundary structure, is connected to ground potential, the grid 24 may be considered as fixed in' potential, and the anode and cathode potentials may be considered as varying in time-phase with respect to grid 24. Conseouently. when such an arrangement is utilized. the double loop 26 produces the desired reversal in phase so that the grid-cathode and the anode-grid cavity voltages have the desired phase relationship necessary to maintain the discharge device. as a whole. in oscillation.

In Fig. 3, I have diagrammatically illustrated a modification of my invention as applied to a high frequency amplifier of the space resonant type which is similar in many respects to the arrangement illustrated in Fig. 1, and corresponding elements have been assigned like reference numerals. In the arrangement of Fig. 3, it will be noted that the metallic boundary 3 is continuous'except for the opening 8, and that additional or separate coupling means need not be provided between the space resonant cavities I and 2. In the arrangement of Fig. 3 I provide means for establishing within the grid-cathode output electrode means.

The embodiment of my invention illustrated in Fig, 3 operates as an amplifier of high frequency voltages or signals supplied by the input electrode means comprising conductors 36 and 31. The operation of the embodiment of my invention from an elementary point of view may be considered in the following manner. The excitation of the grid-cathode cavity 2 by the input electrode means 38 and 31 establishes within the cavity 2 a standing electromagnetic wave due to the tuned or resonant condition of the cavity to the frequency of the input excitation. Resonant slot l4 effects a concentration, of the potential diiference due to the standing wave in cavity 2, across its boundaries and consequently modulates the electron beam transmitted between cathode l5 and anode [-5, so that amplified voltages appear across the horizontal dimensions of the resonant slot H3 in the anode-grid cavity 1. As a result thereof, a standing electromagnetic wave is established within the cavity 2 of amplified value which is delivered to an output or utilization circuit which may be connected to the output electrode means comprising conductors 28 and 29.

It will be obvious to those skilled in the art that the high frequency amplifier shown in Fig. 3 may be employed in a variety of ways. For eX- ample, the device may be employed to amplify weak high frequency signals. In addition, the system may be modified for use as a regenerative amplifier wherein a predetermined component of the output voltage derived .from conductors 28 and 29 is fed back to the input electrode means comprising conductors 36 and 31.

While I have shown'and described my invention as applied to a particular system and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I .claim as new and desire to secure by Letters Patent of the United States is:

l. A high frequency electrical apparatus comprising a pair of wave guides having a common metallic wall and defining a pair of cavity resonators each dimensioned to support standing electromagnetic waves of predetermined frequency, said common metallic wall having an opening therein, each of said wave guides including a transverse wall structure defining a resonator capable of resonance at substantially said predetermined frequency for effecting a concern tration of the electric field incident to the respective standing waves, and means for sustaining high frequency electromagnetic waves in said resonators comprising an anode in one of said resonators, a cathode in the other of said resonators and a grid interposed therebetween, said anode, cathode and grid being mounted in alignment through said opening.

2. A high frequency electrical apparatus comprising a pair of wave guides having a common aperture adjacent said thereby a resonator capable of resonance "at suhgstantially said 'i for sustaining high frequency I Waves in said resonators comprising an anodein metallic wa and. defin naanai o v t r a i eah dimensio e to c r 'fs i electromagnetic waves of predetermined frerqu nc i sa d emm 'n m t Wa n an opening therein, each of s'aidwave guides including a transverse wall structure defining a resonator capa hleof resonance at substantially said predetermined frequency for effecting a concentration of the electricfieldin-cident to the respective standing waves, and means for sustaining hig r quen resonators comprising an anode in one'fof said resonators adjacent the, said'wall structure there'- in, a cathode in the other'of said resonators adjacent the said wall structure therein and a grid conductively attached to said common wall, said anode, cathode and grid being mounted in alignment through said opening,

3. A high frequency electrical apparatus comprisinga pair metallic wall I V F nators each dimensioned to support standing electromagnetic waves of predetermined frequency, said cornmon metallic wall having an opening therein, each of said Wave guides inof Wave guides having a common eluding a transverse wall structure defininga resonator capable of resonance at substantially said predetermined frequency for efiectinga concentration o f the electric ileld incident to the respective stanfingwaves, and 'means for sustaining high frequency electromagnetic waves in "said resonators comprising an anode in one of' said resonat r ositiqn ad a e h Said .w structure thereinwithin the region of said concentrationof electric field therein, a catl iddein the other of said resonators positioned'adjacent the said wall structure therein with the rcgiofriof said concentration of electric field therein, and a grid conductively attached to said common wall, said anode, cathode and grid mounted in alignment through said opening.

4- hi h frequenc elec ri a a atu to prising a .pair of wave guides having a common metallic wall and defining a pair of cavity resonators each dimensioned to support standing electromagnetic waves of .predetermined' 'irecuency, a d mm n. me a l W ha ing an opening therein, each of said wave guides including a transverse ,wall structure having therein an opening and defining predetermined frequency for efiecting a concentration orthe electric fieldincident to the respective standing waves, and means e1ect bm n t c one of said resonators, a cathode in the'other of said resonators and a grid interposed therebetween, said anode, cathode and grid being mounted in alignment through said opening.

prising a pair of wave guides having a common metallic wall and defininga pair or cavity resonators, each dimensioned to support standing of said .wave, guides including a tune adjacent said opening and defining'ther'eby a res onator capable of resonance at substantially ,centration of the electric and incidentf itog the respec tam na. waves an j i r taining high frequency electromagnetic waves in said resonators comprising an anode in one of electromagnetic waves in said and defining a pair of cavity resoe (70 .said predetermined frequencyiforefiectinga con- 5. A high frequency electrical apparatus co ntallic wall and each dimen Said anode; cathode and grid, being mfiuntedin alignment through"saidbp'ening. w

prising a pair of wave guides having acommcn manna Wallanddefining a pair of cavity'resoe haters each'fdimensioned tosupport standing electromagnetic" waves" "of predetermined Sirequency, said common metallic walll'having an 'openingithereinfeach .o'f said wave guidesfincl'udihg" a'trai-i's'versewall structure having therein an ap'ertuIe adjacnt sai opening and defining therehy a resonator capable of'resonance'at sub- "s't'antially' "said predetermined frequency for effecting a concentration 'o'f the electricifield. ineicenv'to the respective standing waves, and riieans for sustaining highifre'quen'cy electromagnetic waves in said" resonators comprising :an 'ar' o de-in one of said resonators positioned adjacent-the said wall structure therein withinz the 'regio'n"of "said concentration of electric. .field therein; a cathode in the other of said resonators positigind' adjacent the said with structurethere;

Within the reg ion'of said concentration of electric field-therein, and a grid conc'liictivelyattached to said Tcom'r'non Walljsaidanodej cathode and grid "mounted in alignment through said 7."A"high frequency electrical apparatus comprising apair'of'tvavguides .of rectangular cross sectionihaving a common metallic iwall and defining a pair of cavity resonators each .dim'ensi nod to support -standing electromagnetic waves of "p're'determined frequency} said common inetallic wall- 'havingan openingtherein; acli of said wave guides including a' pair of transverse walls each "having therein a rectangular aperture on opposite sides of said opening and defining thereby a resonator" structure capable of resoh'a'nc'e' at substantially "said predetermined .i'frediiency for effecting a concentration of the elecjtric -field incident to the respective standing Waves, and means for sustaining.- high frequency electromagnetic J-WEWES in said resonators comopening th'erei'n','eachof said resonators havingfa transv rs wan structured'efininga resonator-floaif le'lfvf -l"sofiahce at S'IJlK'J'Sl;fitnll'jlally said ipredeterminedjireduency for effecting a concentration or lthe'electric fieldl incidentttto; the respective standir'ig'waves, and an electricdischarge Path defined Joy-principal electrodes on opposite sides of said 'comrnon wau within the vicinity, of, said opening and an electro st'atic control means-interp'i js'ed in spaced:relation between said principal electrodes? 9. An electric discharge device, comprising a pair'of cavity resonators having a, icoinnion mes-ioned-to support of predetermined Ii'c wanna rig-an sta :62 Alihigh :irequ'ency electrical apparatus comd ingfa transverse wall structure having therein an aperture and defining thereby a resonator capable of resonance at substantially said predetermined frequency for effecting a concentration of the electric field incident to the respective standing waves, and an electric discharge path type dimensioned to support standing electromagnetic waves of predetermined frequency, said common metallic wall having an opening therein, each of said resonators having a transverse wall structure having therein an aperture and defining thereby a resonator capable of resonance at substantially said predetermined frequency for effecting a concentration of the electric field incident to the respective electromagnetic waves therein, an electric discharge path defined by principal electrodes electrically insulated from said resonators and on opposite sides of said common wall in alignment with said opening and an electro-static control means interposed in spaced relation between said principal electrodes and conductively connected to said metallic Wall, means connected to one of said resonators for extracting output power therefrom, means connected to said principal electrodes for applying a unidirectional potential therebetween, and coupling means connected between said resonators.

11. An electric discharge device comprising a pair of cavityresonators having a common metallic wall and each being of the hollow pipe-typ dimensioned to support standing electromagnetic waves of predetermined frequency, said'common metallic wall having an opening therein, each of said cavity resonators having a transverse wall structure having therein an aperture and defining thereby a resonator capable of resonance at substantially said predetermined frequency and adjacent said metallic wall in the vicinity of-said opening for effecting a, concentration of the electric; field incident to the respective standing waves, an electric discharg path defined by principal electrodes on opposite sides of said common wall in alignment with said opening, electrostatic control means interposed in spaced relation between said principal electrodes and conductively connected to said common wall, and coupling means interconnecting said resonators.

. 12. A high frequency electrical oscillator comprising a pair of wave guides having a common metallic wall and defining a pair of cavity resonators each dimensioned to support standing electromagnetic waves of predetermined frequency, said common metallic wall having an opening therein, each of said wave guides including a transverse wall structure having therein an aperture adjacent said opening and defining thereby a resonator capable of resonance at substantially said predetermined frequency for effecting a concentration of the electric field incident to the respective standing waves, means for sustaining high frequency electromagnetic waves in said resonators comprising an anode in one of said resonators adjacent the said Wall structure therein, a, cath'ode in the other of said resonators adjacent the said wall structure therein,

and a grid conductively attached to said common wall, said anode, cathode and grid being mounted in alignment through said opening, means intercoupling said resonators for interchanging energy therebetween, and means coupled to one of said resonators for extracting energy therefrom.

13. A high frequency electrical amplifier comprising a pair of wave guides having a common metallic wall and defining a pair of cavity resonators each dimensioned to support standing electromagnetic Waves of predetermined frequency, said common metallic wall having an opening therein, each of said wave guides including a transverse Wall structure having therein an aperture adjacent said opening and defining thereby a resonator capable of resonance at substantially said predetermined frequency for effecting a concentration of the electric field incident to the respective standing waves, means for sustaining high frequency electromagnetic waves in said resonators comprising an anode in one of said resonators adjacent the said wall structure therein, a cathode in the other of said resonators adjacent the said wall structure therein, and a grid conductively attached to said common wall, said anode, cathode and grid being mounted in alignment through said opening, means coupled to said other of said resonators for introducing thereto a signal to be amplified, and means coupled to said one of said resonators for extracting an amplified signal therefrom.

14. A high frequency electrical amplifier comprising a pair of Wave guides having a common metallic wall and defining a pair of cavity resonators 'each dimensioned to support standing electromagnetic waves of predetermined frequency, said common metallic wall having an opening therein, each of said wave guides including a transverse wall structure having therein an aperture adjacent said opening and defining thereby a resonator capable of resonance at substantially said predetermined frequency for effecting a concentration of the electrical field incident to the respective standing waves, means for sustaining high frequency electromagnetic waves in said resonators comprising an anode in one of said resonators adjacent the said wall structure therein, a cathode in the other of said resonators adjacent the said Wall structure therein, and a grid conductively attached to said common wall, said anode, cathode and gridbeing mounted in alignment through said opening, means coupled to said other of said resonators for exciting said other of said resonators at its natural resonant frequency, and means coupled to said one of said resonators for extracting energy therefrom.

. JAMES M. LAFFER'I'Y.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

